/* 何を・なぜ: 式、覚え方、確認問題、解き方を一つの視線の流れに配置し、スマートフォンでも迷わず学べるようにする。 */
.swb-decibel-practice { --swb-db-ink: #18324d; --swb-db-blue: #175b9f; display: grid; gap: 1rem; max-width: 800px; margin: 0 auto; color: var(--swb-db-ink); }
.swb-decibel-practice__lead { padding: clamp(1.25rem, 4vw, 2rem); border-radius: 18px; background: #eaf4fc; }
.swb-decibel-practice__label, .swb-decibel-practice__eyebrow { color: var(--swb-db-blue); font-size: .8rem; font-weight: 800; letter-spacing: .08em; }
.swb-decibel-practice__lead h2 { margin: .55rem 0; font-size: clamp(1.4rem, 3vw, 2rem); line-height: 1.35; }
.swb-decibel-practice__lead p { margin: .65rem 0 0; line-height: 1.7; }
.swb-decibel-practice__example { display: grid; gap: .45rem; margin: 1rem 0; padding: .85rem 1rem; border-radius: 10px; background: #fff; list-style: none; }
.swb-decibel-practice__example li { display: flex; flex-wrap: wrap; justify-content: space-between; gap: .5rem; }
.swb-decibel-practice__example strong { color: var(--swb-db-blue); }
.swb-decibel-practice__log-bridge { padding: clamp(1.25rem, 4vw, 1.75rem); border-radius: 18px; background: #fff8e8; }
.swb-decibel-practice__log-bridge h3 { margin: .45rem 0 1rem; font-size: 1.2rem; line-height: 1.5; }
.swb-decibel-practice__log-bridge p { margin: .85rem 0 0; line-height: 1.7; }
.swb-decibel-practice__log-examples { display: grid; grid-template-columns: minmax(0,1fr) minmax(0,1fr); gap: .45rem .8rem; padding: .8rem; border-radius: 9px; background: #fff; }
.swb-decibel-practice__log-examples strong { color: var(--swb-db-blue); }
.swb-decibel-practice__reference { font-size: .9rem; }
.swb-decibel-practice__progress { display: inline-block; padding: .3rem .8rem; border-radius: 99px; background: #fff; font-weight: 700; }
.swb-decibel-practice__step { padding: clamp(1.25rem, 4vw, 1.75rem); border: 1px solid #d9e3eb; border-radius: 18px; background: #fff; box-shadow: 0 6px 20px rgba(24,50,77,.05); }
.swb-decibel-practice__step h3 { margin: .35rem 0 1rem; font-size: 1.3rem; }
.swb-decibel-practice__rule { margin: 0 0 1.2rem; padding: .7rem .85rem; border-left: 4px solid var(--swb-db-blue); background: #f3f8fc; }
.swb-decibel-practice__rule summary { font-weight: 700; cursor: pointer; }
.swb-decibel-practice__rule p { margin: .65rem 0 0; }
.swb-decibel-practice__memory { margin: .8rem 0; line-height: 1.65; }
.swb-decibel-practice__memory strong { display: inline-block; margin-right: .4rem; padding: .15rem .45rem; border-radius: 4px; background: #fff1ce; }
.swb-decibel-practice__step fieldset { min-width: 0; margin: 0; padding: 0; border: 0; }
.swb-decibel-practice__step legend { width: 100%; margin-bottom: .75rem; font-weight: 700; }
.swb-decibel-practice__choices { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: .6rem; }
.swb-decibel-practice__choice { min-height: 3rem; padding: .55rem; border: 1.5px solid #b9cbdc; border-radius: 9px; background: #fff; color: var(--swb-db-ink); font: inherit; font-weight: 700; cursor: pointer; }
.swb-decibel-practice__choice:hover, .swb-decibel-practice__choice:focus-visible { border-color: var(--swb-db-blue); background: #eef6ff; }
.swb-decibel-practice__choice:focus-visible, .swb-decibel-practice__next button:focus-visible { outline: 3px solid #e6a000; outline-offset: 2px; }
.swb-decibel-practice__choice--correct { border-color: #26834a; background: #e9f8ee; }
.swb-decibel-practice__choice--incorrect { border-color: #bd4c43; background: #fff0ee; }
.swb-decibel-practice__feedback { margin: 1rem 0 .2rem; font-weight: 800; }
.swb-decibel-practice__explanation { margin: .2rem 0 0; line-height: 1.7; }
.swb-decibel-practice [hidden] { display: none !important; }
.swb-decibel-practice__next { padding: 1.5rem; border-radius: 18px; background: #18324d; color: #fff; }
.swb-decibel-practice__next p { margin: .45rem 0 1rem; }
/* 何を・なぜ: Topic 20をPOSTするボタンも従来のリンクと同じ見た目・キーボード操作性に保つ。 */
.swb-decibel-practice__next button { display: inline-block; padding: .7rem 1rem; border: 0; border-radius: 8px; background: #fff; color: #18324d; font: inherit; font-weight: 800; cursor: pointer; }
@media (max-width: 520px) { .swb-decibel-practice__choices { grid-template-columns: 1fr; } .swb-decibel-practice__log-examples { font-size: .9rem; } }